The use of an extrusion process for the production of cutting tools made of cemented carbide is known. There are several types of cutting tools that may be produced by such a process, e.g., drills, end mills, reamers, taps, as well as countersinking and counterboring tools. The required cutting tool may be extruded to the desired diameter and length, and then, the necessary chip evacuation flutes are produced.
In some cases, the chip evacuation flutes may be parallel to a longitudinal axis of the cutting tool, as required, for example, in some kinds of reamers. In other cases, the chip evacuation flutes may extend spirally around the longitudinal axis, as required, for example, in other kinds of reamers, and in end mills and drills.
Each of the cutting tools may be provided with an internal cooling channel that extends from its rear portion to its front portion in order to supply cooling liquid to the cutting area. When the cutting tool is provided with helical chip evacuation flutes then, typically, also the cooling channels extend spirally around the longitudinal axis, following the helix of the flutes.
Each of the above described cutting tools comprises a shank portion, in a rear portion thereof, and, a fluted portion extending forwardly from the shank portion. The shank portion is typically in the form of a round rod and serves for holding the cutting tool by a cutting machine or by an adapter.
There are known various methods for the production of the helical flutes and for the production of the spiral cooling channels.
U.S. Pat. No. 6,669,414 to Puide teaches how to manufacture a helix drill by extruding a blank and then sintering the blank. During the extrusion, a mixture is passed through a die which provides a cylindrical shape to the outer peripheral surface of the mixture. A plurality of jaws are disposed downstream of the die for conducting the mixture. Each jaw includes a helical ridge for engaging the outer surface of the extruded material to cause a helical groove to be formed therein which constitutes a chip flute in the tool. During the extrusion, the jaws are moved away from the mixture to terminate formation of the chip groove, whereby a shank portion of the tool is formed. In order to transfer flushing medium from the spindle to the tip of the drill, two flush channels extend through the entire drill.
Another method for producing a drill blank is disclosed in U.S. Pat. No. 7,296,497 to Kugelberg et al. The method comprising extruding a first blank portion (B1) having a free end and external flutes, allowing the extrusion to continue to supply further extruding mass into a cavity (6), the supply completely fills out the external flutes of the first blank portion (B1) to produce a second blank portion (B2) integral with the first blank portion (B1), allowing the extrusion to continue to produce a desired length of the first blank portion (B1), and cutting off the first blank portion (B1) at the end facing away from the second blank portion (B2).
Another method for producing a drill blank is disclosed in U.S. Pat. No. 7,340,978 to Kugelberg et al. The method comprising extruding a mixture in a feed direction by means of a die to form the diameter of the mixture body. The mixture body passes against a chisel which forms a chip flute in the outer periphery of the mixture body by chip-removing machining When the chisel is displaced away from the mixture body, a non-fluted shaft portion is formed. By rotating the mixture body while contacted by the chisel, a helical chip flute can be formed. Alternatively, the body could be twisted after a straight flute has been formed, whereupon the flute becomes helical.
In some cases, it is beneficial to produce a cutting tool from regions having a different structure. Regions having different structures means that they differ by their qualities, for example, one region, typically a peripheral one, may be more wear resistant, whilst another region, typically an inner one, may be tougher and less brittle.
The properties of the cemented carbide materials are determined by, for example, the chemical composition of the ceramic component, the particle size of the ceramic component, the chemical composition of the binder, and the ratio of binder to ceramic component. The different characteristics of the different regions may be differences in; modulus of elasticity, hardness, wear resistance, fracture toughness, tensile strength, corrosion resistance, coefficient of thermal expansion, and coefficient of thermal conductivity.
Methods for producing cutting tools having regions of a different structure are known in the art. Such methods are disclosed, for example, in U.S. Pat. No. 6,511,265 to Mirchandani et al., in U.S. Pat. No. 6,450,739 to Puide et al. and in U.S. Pat. No. 6,274,082 to Nagahora et al. However, in a co-extrusion method, which is a composite technique for a molten metal material, an entire surface of a first material is covered with a second material. Thus, even unnecessary parts are covered, and the characteristics of the first material cannot sufficiently be exhibited. This may be disadvantageous from the standpoint of costs.